In the field of photomechanical process technology, photographic materials with excellent original-producibility, stable processing solutions and simplified replenishment systems are required for the purpose of dealing with diversified and complicated print forms.
Originals employed in line work processes are often composed of phototypeset letters, hand-written letters, illustrations and halftone image photographs. Accordingly, an original may contain a plurality of images having different concentrations and different line widths in combination. Photomechanical cameras and photographic materials suitable for finishing the images from such originals with good reproducibility as well as image-forming methods applicable to such photographic materials are earnestly desired in this technical field. On the other hand, for the photomechanical processes used for producing catalogs or large-sized posters, spread or choke of half-tone photographs is widely effected. In the photomechanical processes using enlarged halftone image, the screen ruling would be coarsened to give blurred photoprints. As opposed to this, in the photomechanical processes for using reduced halftone image, fine dots with an enlarged ratio of lines/inch are to be photographed. Accordingly, an image-forming method with a much broader latitude is desired for the purpose of maintaining the reproducibility of halftone gradation in photomechanical processes.
As the light source for a photomechanical camera, a halogen lamp or xenon lamp is employed. In order to obtain sufficient photographic speed to the light source, the photographic material to be employed in the photomechanical process is generally ortho-sensitized. However, it was found that the ortho-sensitized photographic materials are much more influenced by the chromatic aberration of lens and therefore the quality of the images formed is frequently worsened by such an influence.
As a system of satisfying the demand for the broad latitude, a method is known where a lith-type silver halide photographic material composed of silver chlorobromide (having a silver chloride content of at least 50% or more) is processed with a hydroquinone-containing developer where the effective concentration of the sulfite ion therein is extremely low (generally, to 0.1 mol/liter or less). A line work or halftone image is obtained, having a high contrast and a high blacking density where the image portions and the non-image portions are clearly distinguished from each other. However, the method has various drawbacks. Specifically, since the sulfite concentration in the developer employed in the method is low, development is extremely unstable to aerial oxidation. For the purpose of stabilizing the activity of the processing solution, various means are tried. But the processing speed is extremely slow, and the working efficiency is poor at present.
Accordingly, an improved image-forming system is desired, which is free from the instability of the image formation in the above-mentioned development method (lith-development system) and which may be processed with a processing solution having an excellent storage stability to obtain photographic images having super-high contrast photographic characteristics. One example is a system of forming a super-high contrast negative image having a gamma value of more than 10, proposed for example in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. There, a surface latent image-type silver halide photographic material containing a specific acyl hydrazine compound is processed with a developer which has an excellent storage stability and which contains a sulfite preservative in an amount of 0.15 mol/liter or more, under a pH value of from 11.0 to 12.3.
The proposed image-forming system is excellent in that an image with a sharp halftone dot image quality is formed, the process proceeds stably at a high speed, and the reproducibility of the original used is good. However, a further improved system with a further elevated original reproducibility is still desired for the purpose of satisfactorily dealing with diversified print forms.
JP-A-61-213847, JP-A-64-72140, JP-A-2-287532, JP-A-2-293736, JP-A-2-301743 and JP-A-2-304433 (The term "JP-A" as used herein means as "unexamined published Japanese patent application") each mention a photographic material containing a redox compound capable of releasing a photographically useful group by oxidation for the purpose of improving the quality of the image to be formed thereon.
JP-A-62-222242, JP-A-62-237443, JP-A-62-237444, JP-A-63-296033 and JP-A-1-187542 each mention a silver halide photographic material containing a hydrazine compound, in which the swelling rate and the kind of the hardening agent to be therein play an important role in improving the photographic characteristics and the image quality and in preventing formation of black peppers.
European Patent Application No. 452848A discloses that swelling of the emulsion layer in a photographic system containing a redox compound capable of releasing a development inhibitor by oxidation is important for the image quality of the system. In the system, however, there is the problem that the image quality as well as the long-time storage stability against the formation of black peppers often deteriorate, depending upon the selected hardening agent or the water content in a gelatin layer.